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Jia N.,China Power Engineering Consulting Group Corporation
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering

Based on the concept of mobilized angle of internal friction, the coefficient of at-rest earth pressure from limited coarse backfill K 0 is obtained after the analysis of the Mohr's cycle. A comparison is made with Jaky's formula for half infinite soil mass K 0J and active earth pressure from limited backfill K a. It is found that K 0 is close to or smaller than K 0J, when the internal friction angle between the rock face and backfill δ r is equal to that of backfill ψ. K 0 is not only influenced by ψ and inclination of the rock face, but also by δ r; K 0 may be larger or smaller than K 0J, when δ r is smaller than ψ; K 0 and K a decrease with the increase of the inclination of the rock slop; and K 0 is larger than K a. To make the rock face rough and to adopt bench excavation are both effective methods to reduce the at-rest earth pressure from the limited backfill. A design graph is given at the end of the paper. Source

Xu S.-Q.,China Power Engineering Consulting Group Corporation
Journal of Railway Engineering Society

Research purposes: As a result of the limitation of engineering site condition, jacking construction method is the only method to be adopted for the large-span curve concrete bridge. For the concrete box girder, which is 250 000 kN in weigh, 213 m in top range and 920 m in radius, the center line in the process of pushing trajectory and the size of the temporary pier horizontal force are the key issues for the design and construction of box girder pusher which is in big tonnage and long range curve. This paper is intended to find ways to solve these problems. Research conclusions: Based on the research on the pushing force and motion of main girder in process of Shangdi Bridge single cable plane curve of prestressed concrete cable-stayed bridge jacking on Beijing-Xinjiang Highway, it can reach the following conclusions: (1) Put forward a new method of the construction of complex curve of concrete box girder, by which it can simplify the design of the ramp and spacing device, and control pusher track of the complex curve girder. (2) Because two-point limit structure is statically determinate system in the horizontal plane, it can be calculated accurately the level of the working condition of the limit force pushing process. And the temporary pier horizontal reaction greatly reduced to the only 1.2‰ of pushing weight, which provides the technical support for the construction security of weight of the complex curve girder pusher. (3) Two-point limit method is suitable for the complex curve prestressed concrete box girder bridge construction of roads, railways and municipal engineering which using the jacking method. Source

Guo Y.-T.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang C.-H.,CAS Wuhan Institute of Rock and Soil Mechanics | Fu J.-J.,China Power Engineering Consulting Group Corporation
Yantu Lixue/Rock and Soil Mechanics

With the project of Jintan underground gas storage, taking the cavity actual bearing conditions as the object of study, carrying out unloading confining pressure test of salt rock under different conditions, the complete stress-strain curves, deformation characteristics are obtained. The test results show that axial and radial strains increase slowly in the initial stage of unloading confining pressure; and the relation between strain and confining pressure is linear. Along with the confining pressure continuous decrease, axial and radial strain values increase sharply. Comparing the loading and unloading curves, under the conditions of the same maximum principal stress, when the unloading confining pressure is the same as triaxial compression pressure value, the axial and radial strains variations are larger than that of loading conditions. Under the same initial stress conditions, the changing magnitude of stress required for rock failure is less than that of triaxial compressive process. It is shown that the plastic deformation of salt rock is different from hard rock of brittle failure under unloading confining pressure. The conclusion can be useful in underground gas storage engineering stability analysis and gas injection/extraction process. Source

Huang J.-J.,Tsinghua University | Huang J.-J.,China Power Engineering Consulting Group Corporation | Hu H.-Y.,Tsinghua University | Wu Y.-H.,Tsinghua University | And 2 more authors.

Antibiotic-resistant bacteria are an emerging threat to public health during drinking water consumption and reclaimed water reuse. Several studies have shown that the proportions of antibiotic-resistant bacteria in waters may increase when exposed to low doses of UV light or chlorine. In this study, inactivation of tetracycline-resistant Escherichia coli and antibiotic-sensitive E. coli by UV disinfection and chlorination was compared to determine the tolerance of tetracycline-resistant E. coli to UV light and chlorine, and tetracycline resistance of a tetracycline-resistant E. coli population was studied under different doses of the disinfectants. Our results showed that relative to antibiotic-sensitive E. coli, tetracycline-resistant E. coli had the same tolerance to UV light and a potentially higher tolerance to chlorination. The mortality frequency distributions of tetracycline-resistant E. coli exposed to tetracycline were shifted by both chlorination and UV disinfection. When compared to the hemi-inhibitory concentrations (IC50) of tetracycline-resistant E. coli with no exposure to UV or chlorination, the IC50 of tetracycline-resistant E. coli treated with tetracycline was 40% lower when inactivation by UV light or chlorination reached 3-log but was 1.18 times greater when inactivation by chlorination reached 4.3-log. Chlorination applied to drinking water or reclaimed water treatment may increase the risk of selection for highly tetracycline-resistant E. coli. © 2012 Elsevier Ltd. Source

Zhao B.,Tsinghua University | Yu Q.,Tsinghua University | Sun W.,China Power Engineering Consulting Group Corporation
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering

In order to reduce the power circulating flow in bi-directional full-bridge DC-DC converters, this paper analyzed the backflow power characteristic of converter. On this basis, the paper presented a dual-phase-shifting control method. The operation principle of the dual-phase-shifting control and the operation stages of the converter were analyzed in the paper. By establishing mathematical models of transmission power and backflow power, the paper comparatively analyzed control performances of the traditional phase-shifting control and the dual-phase-shifting control. At last, experimental results verify the excellent performance of the dual-phase-shifting control. © 2012 Chinese Society for Electrical Engineering. Source

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